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Thread Subject:
Solution of differential equations.

Subject: Solution of differential equations.

From: Soubhik S

Date: 27 May, 2010 06:56:29

Message: 1 of 5

I am trying to solve the following set of differential equations:

y1'=x1-x3-x4-x5
y2'=-x1-x5+x6+x7
y3'=-x1-x2-x4-x6
y4'=-x2-x3
y5'=x1+x5-x6-x7
y6'=x4+x6-x7

where x's are as given below
x1=k1*y2*y3
x2=k2*y3*y4
x3=k3*y1*y4
x4=k4*y1*y3
x5=k5*y1*y2
x6=k6*y3*y5
x7=k7*y5*y6

here, k1,k2,k3,k4,k5 and k6 are all known constants

Sir/Ma'am
can anyone please guide me as to how to solve this problem using
matlab,as I don't have any clue.

Subject: Solution of differential equations.

From: Torsten Hennig

Date: 27 May, 2010 07:30:54

Message: 2 of 5

> I am trying to solve the following set of
> differential equations:
>
> y1'=x1-x3-x4-x5
> y2'=-x1-x5+x6+x7
> y3'=-x1-x2-x4-x6
> y4'=-x2-x3
> y5'=x1+x5-x6-x7
> y6'=x4+x6-x7
>
> where x's are as given below
> x1=k1*y2*y3
> x2=k2*y3*y4
> x3=k3*y1*y4
> x4=k4*y1*y3
> x5=k5*y1*y2
> x6=k6*y3*y5
> x7=k7*y5*y6
>
> here, k1,k2,k3,k4,k5 and k6 are all known constants
>
> Sir/Ma'am
> can anyone please guide me as to how to solve this
> problem using
> matlab,as I don't have any clue.

help ode15s

Best wishes
Torsten.

Subject: Solution of differential equations.

From: Soubhik S

Date: 27 May, 2010 07:59:12

Message: 3 of 5

actually,I wanted a symbolic solution,in terms of y's,not a numeric
solution

Subject: Solution of differential equations.

From: Torsten Hennig

Date: 27 May, 2010 08:24:11

Message: 4 of 5

> actually,I wanted a symbolic solution,in terms of
> y's,not a numeric
> solution
>

For a linear system of ODEs: ok.
For a nonlinear system like yours : impossible.

Best wishes
Torsten.

Subject: Solution of differential equations.

From: Steven Lord

Date: 27 May, 2010 17:43:58

Message: 5 of 5


"Soubhik S" <soubhik15@gmail.com> wrote in message
news:4f153249-9e4e-4ec2-9528-9b8a90c8a8da@23g2000pre.googlegroups.com...
> actually,I wanted a symbolic solution,in terms of y's,not a numeric
> solution

You can try DSOLVE from Symbolic Math Toolbox, but depending on the
complexity of your system it may not be able to find a solution. Look at
ODE45 to find a numeric solution if the symbolic solution approach fails.

--
Steve Lord
slord@mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

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